In common aircraft, grey water, i.e. water from sinks and galleys, may be discharged overboard through a so-called “drain mast”, which is a heated nozzle at the bottom side of the aircraft fuselage, if they are suitable for this. Contrary to this, black water, which is wastewater from the toilets of the aircraft, is collected in a so-called “waste tank” or wastewater collection tank and is eventually disposed of on ground. For conveying the black water into the wastewater collection tank, the aircraft comprises a source of negative pressure, which generates a negative pressure at a lavatory, in order to suction the arising wastewater of and to suction it into the wastewater collection tank through the negative pressure. During the suctioning of arising wastewater of a toilet on board, noise emissions may occur. Due to these noise emissions it is refrained from using a source of negative pressure for suctioning grey water into the wastewater collection tank, since respective noise emissions are to be prevented in particular in the galley.